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A quarter-million years of paleoenvironmental change at Bear Lake, Utah and Idaho

By
Darrell S Kaufman
Darrell S Kaufman
Department of Geology, Box 4099, Northern Arizona University, Flagstaff, Arizona 86011, USA
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Jordon Bright
Jordon Bright
Department of Geology, Box 4099, Northern Arizona University, Flagstaff, Arizona 86011, USA
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Walter E Dean
Walter E Dean
U.S. Geological Survey, Box 25046, MS 980 Federal Center, Denver, Colorado 80225, USA
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Joseph G Rosenbaum
Joseph G Rosenbaum
U.S. Geological Survey, Box 25046, MS 980 Federal Center, Denver, Colorado 80225, USA
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Katrina Moser
Katrina Moser
University of Western Ontario, Department of Geography, London, Ontario N5Y 2S9, Canada
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R. Scott Anderson
R. Scott Anderson
Center for Environmental Sciences and Education, Northern Arizona University, Flagstaff, Arizona 86011, USA
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Steven M Colman
Steven M Colman
Large Lakes Observatory and Department of Geological Sciences, University of Minnesota, Duluth, Minnesota 02543, USA
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Clifford W Heil, Jr.
Clifford W Heil, Jr.
School of Oceanography, University of Rhode Island, South Ferry Road, Narragansett, Rhode Island 02882, USA
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Gonzalo Jiménez-Moreno
Gonzalo Jiménez-Moreno
Center for Environmental Sciences and Education, Northern Arizona University, Flagstaff, Arizona 86011, USA
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Marith C Reheis
Marith C Reheis
U.S. Geological Survey, Box 25046, MS 980 Federal Center, Denver, Colorado 80225, USA
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Kathleen R Simmons
Kathleen R Simmons
U.S. Geological Survey, Box 25046, MS 980 Federal Center, Denver, Colorado 80225, USA
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Published:
May 2009

A continuous, 120-m-long core (BL00-1) from Bear Lake, Utah and Idaho, contains evidence of hydrologic and environmental change over the last two glacial-interglacial cycles. The core was taken at 41.95°N, 111.31°W, near the depocenter of the 60-m-deep, spring-fed, alkaline lake, where carbonate-bearing sediment has accumulated continuously. Chronological control is poor but indicates an average sedimentation rate of 0.54 mm yr‒1. Analyses have been completed at multi-centennial to millennial scales, including (in order of decreasing temporal resolution) sediment magnetic properties, oxygen and carbon isotopes on bulk-sediment carbonate, organic- and inorganic- carbon contents, palynology; mineralogy (X-ray diffraction), strontium isotopes on bulk carbonate, ostracode taxonomy, oxygen and carbon isotopes on ostracodes, and diatom assemblages. Massive silty clay and marl constitute most of the core, with variable carbonate content (average = 31 ± 19%) and oxygen-isotopic values (δ18O ranging from ‒18‰ to ‒5‰ in bulk carbonate). These variations, as well as fluctuations of biological indicators, reflect changes in the water and sediment discharged from the glaciated headwaters of the dominant tributary, Bear River, and the processes that influenced sediment delivery to the core site, including lake-level changes. Although its influence has varied, Bear River has remained a tributary to Bear Lake during most of the last quarter-million years. The lake disconnected from the river and, except for a few brief excursions, retracted into a topographically closed basin during global interglaciations (during parts of marine isotope stages 7, 5, and 1). These intervals contain up to 80% endogenic aragonite with high δ18O values (average = ‒5.8 ± 1.7‰), indicative of strongly evaporitic conditions. Interglacial intervals also are dominated by small, benthic/tychoplanktic fragilarioid species indicative of reduced habitat availability associated with low lake levels, and they contain increased high-desert shrub and Juniperus pollen and decreased forest and forest-woodland pollen. The 87Sr/86Sr values (>0.7100) also increase, and the ratio of quartz to dolomite decreases, as expected in the absence of Bear River inflow. The changing paleoenvironments inferred from BL00-1 generally are consistent with other regional and global records of glacial-interglacial fluctuations; the diversity of paleoenvironmental conditions inferred from BL00-1 also reflects the influence of catchment-scale processes.

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Contents

GSA Special Papers

Paleoenvironments of Bear Lake, Utah and Idaho, and its catchment

Edited by
Joseph G. Rosenbaum
Joseph G. Rosenbaum
U.S. Geological Survey, Box 25046, MS 980 Federal Center, Denver, Colorado 80225, USA
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Darrell S. Kaufman
Darrell S. Kaufman
Department of Geology, Box 4099, Northern Arizona University, Flagstaff, Arizona 86011, USA
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Geological Society of America
Volume
450
ISBN print:
9780813724508
Publication date:
2009

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